Large Scale Deformation Monitoring Of Mine Based On High Resolution SAR Images

China is a big country of mining, it’s no doubt that mining of mineral resources will lead to surface subsidence, aserious threat to the safety of buildings,roads,reservoirs and other facilities. Therefore, it is necessary to monitor the change of deformation in the mining process effectively and comprehensively, in real time.At present, the mine monitoring in our country usually rely on the traditional meas of measurement, such as GPS and leveling, which have high accuracy, but they are based on discrete points, can neither realize the frequently monitoring with large area nor provide the overall deformation trend of mines. In addition, these methods usually require staff to on-site monitoring, which will undoubtedly pose a threat to the personal safety of measuring staff.Synthetic aperture radar interferometry(InSAR) developed in 1960 s, is a new type of space telemetry technology, which has advatages on high precision, high resolution and no contact to ground observation. But there are some limitations in this technology, such as low resolution InSAR technology is greatly affected by temporal decorrelation and atmospheric effects, in areas with high vegetation coverage, alot of SAR images can not generate interferogram or the interferogram quality is very poor.In addition, in the mining areas with large sacle subsidence, the phase gradient caused by deformation in the differential interferograms is often beyond the measurable range.SBAS technology developed on the basis of this, can realize the small deformation time series analysis, then monitor the ground surface subsidence with a long time, but this technique can only obtain the ground deformation of the radar line of sight(LOS).For the deformation monitoring in the horizonatl direction, the offset-tracking and the Split-band interferometry technology can be used. However, the research degree of theses two technologies is relatively low. In this paper, for In SAR monitoring of large scale deformation in the mining area, the following researches are carried out:1) The basic principle and data processing procedure of SBAS technology are introduced. Take the Bingham copper mine in the United States as the research object,collected 9 SAR datas that coverage the Bingham copper mine in America and obtained by PALSAR sensor. By setting the time limit threshold as 3 years and the spatial baseline threshold as 1500 m, the 10 interferograms with high coherence quality are selected, DInSAR processing were conducted to them, through the matlab programming extracted the time sequence of settlement information in the LOS direction from 2007 to 2011, monitoring the maximum settlement of 0.8m. Through comparison with existing GPS and precise leveling observation data, the results of the two methods mutual agreement. In addition, the two region with larger deformation are monitored by SBAS technology, and their variable rate have an increasing trend,which is consistent with the mining process and subsidence prediction results. It isvisible that SBAS technology can monitoring the subsidence in the LOS direction with long time span and large scale.2) The offset-tracking technology and the Split-band interferometry thechnology are discussed in terms of the ability to monitor the horizontal subsidence. First of all,the basic principle and data processing flow of the offset-tracking and split-band interferometry are described in detail, then take Bingham copper mine as the research object, collect two PALSAR datas with high coherence covering this region,offset-tracking and split-band interferometry are conducted to the two images.Through theoretical analysis and comparison and verification, the results show that the split-band interferometry technique has more advantages than the offset-tracking technique in terms of accessing the precision azimuth deformation.3) A method named Split-band interferometry based timing analysis is put forward, which can solve the problem of low coherence effect monitoring accuracy,and realize monitoring the large scale surface subsidence of mine areas in azimuth direction. Firstly, we found that the low coherence is the main factor to limit the monitoring accuracy of the split-band interferometry technique by comparing the coherence coefficient distribution of the split-band and the original interferometry.Therefore, this paper presents a split-band interferometry based timing analysis algorithm. Based on seven scenes PALSAR datas covering Bingham copper mine,according to the baseline set theory, by setting the time and vertical baselines threshold for 3 years and 1500 m, 10 subband interferograms were selected, then using matlab to analyze, the subsidence information in azimuth direction within 4 years were subtracted, and compare with the existing observation data, it is found that the results are consistent. In addition, analyze the two large deformation region monitored by SBAS technology in the azimuth direction, the trend of azimuth deformation and the deformation trend in LOS direction are consistent, the accuracy of this method is proved again. The experiment demonstrate it is feasible to use this method to accurately monitor the mining surface subsidence with long time span, and the large scale in azimuth direction.